The present invention relates to the hydroforming of a material in a two-stage operation so that the material is first preformed followed by final forming into the desired final shape.
Hydroforming is a procedure for shaping material, usually a metal, within a closed mold by subjecting the material to high fluid pressure, as the fluid pressure of a liquid, so that the material is permanently deformed against a mold surface.
U.S. Pat. No. 5,157,969 to Roper, U.S. Pat. No. 5,372,027 to Roper et al., U.S. Pat. No. 5,715,718 to Rigsby et al., U.S. Pat. No. 5,799,524 to Schafer et al. are all examples of hydroforming of materials. The '524 and '718 patents discuss hydroforming of a hollow workpiece, but neither reference teaches preforming the workpiece prior to final forming by using the pressure internally.
In addition to the foregoing, the following U.S. patents show a two platen clamp having tiebars engaged by rotating hydraulic clamp pistons: U.S. Pat. Nos. 5,624,695, 5,645,875 and 5,620,723 all to Glaesener et al. and U.S. Pat. No. 5,868,989 to Glaesener.
It is a principal object of the present invention to provide an improved process and apparatus for forming a shaped article.
It is a further object of the present invention to provide a process and apparatus as aforesaid which efficiently and expeditiously forms a shaped article by a two stage operation including finally hydroforming a hollow article at high internal pressure.
Further objects and advantages of the present invention will appear hereinbelow.